The Echo colonnade was built around 350 BC and it was the eastern boundary of the Sacred Altis (precinct) of Olympia. With its construction, the Stadium was isolated from the Altis. Its name is due to its acoustics, since the sound was repeated seven times. That is why it was also called "Eptaechos" (the sound was repeated seven times). Its interior had painting decoration of great painters of the time and was also called "Poikili Stoa". It is 98 meters long and consists of an external Doric colonnade with 44 columns and an inner one that has not been elucidated whether it was Ionian or Corinthian.In the middle of the 3rd century. B.C. in front of the Stoa of Echo was built the monument of Ptolemy II and Arsinoe. This monument consists of a large stone platform 20 m long and 4 m wide. At its two ends there were two Ionic columns, 8.89 m high, on which the gold-plated statues of Ptolemy and Arsinoe were placed. From the impressive monument, the stone crypt and parts of the Ionic columns are preserved.